The Summer Triangle—high in the western sky—forms an asterism (identifiable shape), not a constellation. It shares the night sky with the Great Square—another asterism—which forms the body of Pegasus the flying horse. The Big and Little Dippers are also asterisms—identifiable shapes within Ursa Major and Ursa Minor.

Twilight extends the period of daylight in three stages at each end of the day. Morning twilight begins with astronomical twilight—about 1-1/2 hours (nearly 2 during summer months) before sunrise—as the eastern horizon brightens. Nautical twilight continues—as the overhead sky turns blue and color returns to the surrounding landscape—for another 30-40 minutes. The final stage—civil twilight—provides adequate light for most outdoor activities for the half hour before the sun crests the horizon. The opposite progression occurs after sunset.

MOON HAPPENINGSOctober 1 – Bright evening skies until after midnight when the waxing first quarter moon sets.October 8– Bright skies throughout the night after the full moon (at 4:51am) rises at 7:09pm. October 15– Dark evening skies until after midnight when the waning last quarter moon rises.October 23– Dark sky period for several days before and after the new moon at 3:57pm.October 30–Bright evening skies until after midnight when the waxing first quarter moon sets.
(The time of moonrise and moonset assumes a flat horizon. Actual time may vary.)

TOTAL LUNAR ECLIPSEOctober 8 - This month’s full moon will be obscured by the earth’s umbral (primary) shadow during the morning’s pre-dawn hours. Totality lasts one hour. Astronomical twilight begins to brighten the eastern sky about one-half hour after totality ends. The moon regains its full exposure about 45 minutes before sunrise.

October 23 – Lunar eclipses are always paired with solar eclipses, so a solar eclipse will occur on the afternoon of October’s new moon. Since the sun will not pass under the center of the moon’s umbra, only 42.8% of the sun will be obscured by the moon’s shadow as seen from Moab. Anyone who still has special solar filter glasses from the last eclipse can safely view this eclipse. Others should use a card or foil with a pinhole in the center to project the image of the partially obscured sun onto a flat surface.

Eclipse Begins 3:13pm
Maximum Eclipse 4:32pm
Eclipse Ends 5:42pm

VISIBLE PLANETSJupiter – The lone planet of the morning sky rises a few hours after midnight with Cancer and climbs high into the eastern sky before astronomical twilight brightens the eastern horizon. Jupiter rises about four minutes earlier each night. By October 13 it has drifted into Leo. A waning crescent moon passes below Jupiter on the mornings of October 17 and 18. (Magnitude -2.0)

Mars – Find Mars along the western horizon for about an hour after astronomical twilight fades from the night sky. It rises about one minute earlier each day. Look for a red disk below Ophiucus until October 22 after which Mars moves into Sagittarius. A waxing crescent moon moves up below Mars from the western horizon on October 26. Watch them over the next few nights. (Magnitude +0.9)

Saturn – Saturn’s golden orb sits low on the southwestern horizon. By midmonth it will be lost in the glare of the setting sun as it approaches next month’s pass around the far side of the sun. (Magnitude +1.4)

Note: Apparent magnitude values range from -4 to +6 for most planets and visible stars. The lower the value the brighter the object. A decrease of 1.0 magnitude is 2.5 times brighter.

Primary Sources: USGS; U.S. Naval Observatory; Your Sky at http://www.fourmilab.ch/yoursky/
To find out when the space shuttle and International Space Station are visible from your location,
go to: http://spaceflight.nasa.gov/realdata/sightings/index.html and click on Sighting Opportunities.

Hold your hand at arm’s length to measure apparent distances in the sky. The width of the little finger approximates1.5̊. Middle, ring, and little finger touching represent about 5 ̊. The width of a fist is about 10 ̊. The fist with the thumb extended at a right angle equals 15 ̊. The hand stretched from thumb to little finger approximates 20 ̊-25 ̊. The diameter of both the full moon and the Sun spans only 0.5 ̊. Adjust for the size of your hand.

The star chart approximates the sky from astronomical twilight to midnight. As the night and month progresses, the constellations shift toward the northwest. The celestial equator is measured in hours (h).
The ecliptic is measured in degrees

Note: Hold your hand at arm’s length to measure apparent distances in the sky. The width of the little finger approximates 1.5̊. Middle, ring, and little finger touching represent about 5̊. The width of a fist is about 10̊. The fist with the thumb extended at a right angle equals 15̊. The hand stretched from thumb to little finger approximates 20̊-25̊. The diameter of both the full moon and the sun spans only 0.5̊. Adjust for the size of your hand.